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Energy
Published in William Bolton, Engineering Science, 2020
Alternatively, we can consider that the force can be resolved into two components, namely F cos θ in the direction of the displacement and F sin θ at right angles to it. There is no displacement in the direction of the F sin θ component and so it does no work. Hence the work done by the oblique force is solely due to the F cos θ component and so is, as before, (F cos θ) × s.ExampleA barge is towed along a canal by a tow rope inclined at an angle of 20° to the direction of motion of the barge. Calculate the work done in moving the barge a distance of 100 m along the canal if the pull on the rope is 400 N.We have an oblique force and so, since the displacement in the direction of the force is 100 cos 20°, the work done = 400 × 100 cos 20° and so 37.6 kJ.
Compaction of soils
Published in Alan J. Lutenegger, Soils and Geotechnology in Construction, 2019
Sheepsfoot rollers have been used since the 1900s to compact fine-grained soils. They may be towed behind a rubber-tired tractor or a crawler tractor. As shown in Figure 4.28, they consist of a large drum with feet or pads welded to it. The size, shape, spacing, and length of the individual feet varies depending on the manufacturer and the application. Some feet are square, while others are round, as shown in Figure 4.29. Some feet have a tapered geometry, which produces lateral compaction between the feet and can improve efficiency. The feet are usually offset on the drum to get better coverage. Sheepsfoot rollers are available in single-drum or double-drum configurations and are a common piece of construction equipment for highway and earth-dam construction throughout the world.
In-Situ Burning an Update
Published in Merv Fingas, In-Situ Burning for Oil Spill Countermeasures, 2018
A number of ideas have been proposed to replace fire-resistant booms when burning oil on water. Marine Research Associates has proposed the use of modified barges to contain the oil for burning. Some of these are shown in Figure 1.49 (Marine Research Associates 1998). One concept involves cutting the centre tanks from a barge or extensively modifying a barge without centre tanks so that only wing tanks remain. The barge would be towed at the apex of a boom and oil contained within the centre of the barge, as illustrated in Figure 1.49a. A design for a barge with inflatable sides is illustrated in Figure 1.49b, and another design which uses forced air to enhance burning is illustrated in Figure 1.49c. These concepts and several variations of these are analysed in detail in the report, which shows that the barge concepts should provide a stable burn platform and a more extended life over a fire-resistant boom. These concepts would be very costly to implement and result in large, heavy devices.
Turning DDT into ‘Didimac’: Making insecticide products and consumers in British farming after 1945
Published in History and Technology, 2022
Alongside the work done to turn raw chemicals into pesticide treatments, Pest Control Ltd needed to master the operation of spraying equipment, which for field crops frequently comprised a large boom sprayer that could be towed or attached to a tractor. Spraying insecticides and weedkillers required consideration of a host of issues: nozzle type, droplet size, boom height, spray pattern and spraying angles. An insecticide had to be mixed in the correct proportion with water by operators in the field and then run through a machine at the right rate to give good coverage. This was not necessarily a straightforward process, as shown by this article on the problems facing farmers, from 1949, To the scientist in his laboratory, one part in 1,000, 10,000 or more, presents no difficulty, but to the farmer with his primitive measuring tins, a gallon to an acre is frightening. Things of such power as this seem almost atomic and he fears that the smallest error will certainly lose him his crop and a major one blow him sky high.The apparent slowness by farmers, landowners and horticulturists to adopt many of the new products of the agricultural chemist must have been disappointing to the discoverers of these wonders. But this reluctance to try something new is not so much conservatism, but rather that most of these new products have presented mechanical problems difficult for the would-be user to solve. 68
Nonlinear static finite element analysis of sinking a floating pipeline to the bottom in calm water
Published in Journal of the Chinese Institute of Engineers, 2021
In this paper, a nonlinear static finite element analysis is presented for simulating the process of laying a floating pipeline down to seabed in calm water. The soil–pipe interaction elements, fully submerged pipe elements, partially submerged pipe elements, and floating pipe elements, and their stiffness matrices have been introduced. Also, the load stiffness matrix associated with hydrostatic pressure has been illustrated and considered in the analysis. Then, an incremental iterative procedure has been developed to analyze large deformation of the pipeline during the sinking process and to take into account soil–pipe interaction. Three numerical examples have been provided to show the capabilities of the proposed analysis to model the continuous float-and-sink procedure of the pipeline. The paper emphasizes the modeling of water weight distribution inside the pipeline and boundary conditions related to an offshore tugboat. The results show that the solutions of the final deformed geometries of the pipeline using different ways of distributing filled-in water loads can converge, and the fixed-simple and fixed-free boundary conditions can be utilized to appropriately simulate the sinking process of a floating pipeline towed by a tugboat.
Robust lateral control of long-combination vehicles under moments of inertia and tyre cornering stiffness uncertainties
Published in Vehicle System Dynamics, 2019
Maliheh Sadeghi Kati, Hakan Köroğlu, Jonas Fredriksson
For mechanical systems, the descriptor form is usually obtained through the Lagrangian formulation, which is an alternative to the Newtonian approach. A major advantage of the Lagrangian formulation over Newtonian approach is that it can eliminate constraints and coupling forces between the units at the linking joints with a proper choice of the generalised coordinates [23]. Therefore in this study, a linear single-track model of the A-double is derived with five degrees of freedom (i.e. lateral and yaw motions of the tractor and three yaw motions of the towed units caused by the articulation joints) based on the Lagrangian formulation [24,25]. In the derivation of the proposed linear model, the longitudinal velocity is considered as a constant value and all angles are assumed to be small.